Police are investigating claims 15-year-old Jai Morcom, who died after a schoolyard brawl on the New South Wales north coast, was being bullied.

Jai died in hospital on Sunday after suffering head injuries allegedly during a fight at Mullumbimby High School last Friday.

Police say the incident started as a fight between two boys, and that Jai was a bystander.

Today students staged a mass walkout to protest the death of their friend.

Some students and parents are calling for the sacking of the principal, saying violence at the school is out of control.

Acting Superintendent Owen King says police will spend the next few days interviewing staff and witnesses of the fight.

"We have the assistance of the school response unit, our school liaison police and our homicide unit are overseeing the investigation," he said.

"The expertise that they provide will assist us in coming up with an outcome so that we can prepare that brief for the coroner."

One mother Sara Lehane says she warned the school principal about a bullying problem prior to Jai's death.

Ms Lehane says she withdrew her son from the school because of concerns about violence.

"Everyone denies it and that's why I'm putting up flowers. People are putting up flowers because we're saying this can't be denied any more," she said.

"As a culture, as a community, it cannot be denied any more.

"I have a kid that I withdrew from the school due to bullying and put him in distance education and actually told the principal something like this was going to happen unless he actually addressed things."

Bullying denied

But NSW Secondary Principals Association president Jim McAlpine is keen to stress that so far the investigation has not confirmed this was a case of school bullying.

"I'm not sure on the data that's available at the moment that this was a case of bullying," he said.

"It appears it was a case of push and shove in the playground to begin with rather than bullying, which is sort of ongoing harassment of a particular student, making them a victim.

"There's nothing that I'm aware of that would suggest that's the case in this particular situation."

He also does not think the protests are a vote of no confidence in the principal.

"I think we need to take that with a little bit of - not scepticism - but understanding that grief expresses itself in different ways," he said.

"I think it's really is important that we wait to find out what the inquiry might discover in relation to the death of young Jai, what were the circumstances and to ensure that we are speaking on a factual basis rather than responding to rumours and speculation."

A parents' group has also voiced its support for the principal.

The P and C Association has released a statement saying it supports the principal and staff at the school.

A spokesman for the Department of Education says the walkout was a peace march and most students have returned to class.

In mourning

Jai's mother Kim says she is devastated by her son's death.

"There is no words to describe how we feel. The whole family and the whole community, friends, everybody, devastated," she said.

She wants to know how it could be that her son could die in such terrible circumstances.

"You say goodbye. It is a normal morning. You know, 'got your lunch money? See you later'," she said.

"You don't expect anything like this to happen ever."

Some reports have suggested Jai had a pre-existing medical condition, but police say that is not true.

His family also rejects the suggestion.

Meanwhile, NSW Education Minister Verity Firth says Mullumbimby High School will be given all the resources it needs to cope with the death.

Ms Firth says counsellors will be provided for students and staff for as long as needed, and has also agreed to the principal's request for a third deputy.